The present invention relates to wireline borehole operations, particularly borehole logging and perforating operations using a stinger for extending, moving, and positioning wireline tools in highly deviated wells.
In the ever continuing search for oil and gas, as well as the development of oil and gas fields for production, more and more wells are being drilled today with significant portions of the borehole deviating substantially from the more traditional vertical orientation. In offshore production, for example, it is usually more economical to have a single drilling and production platform serving a large number of wells than to have individual platforms for each well. Accordingly, many of the boreholes drilled from such a shared or common platform must travel substantial horizontal distances to reach the region of the reservoir intended to be logged or produced. Other conditions calling for highly deviated boreholes include shallow depth gas production, exploration and production under shipping fareways, and special circumstances imposed by deed restrictions or by governmental agencies on surface production facilities in certain areas. Such boreholes have increasingly long, highly deviated ramps, often above 70.degree. angles of deviation and lengths of 16,000 feet or more.
To determine various physical parameters of the formations adjacent the borehole, and to perforate boreholes for production, traditional and conventional well-logging tools and perforators are commonly suspended and lowered into the borehole on a well-logging cable (a "wireline") to the area under consideration. In such highly deviated boreholes, however, gravity cannot be relied upon to lower the well logging tool and to pull the wireline cable along behind the tool.
Another technique for moving subsurface well equipment, particularly when pipe or tubing is available in the well, is to pump the equipment through the tubing by fluid flow therein. U.S. Pat. No. 3,727,693 (issued Apr. 17, 1973 to Tausch et al.), for example, shows a two-stage locomotive system for moving well equipment through a curved entrance tubing into a well. The equipment is pushed ahead of the locomotives through tubing which is itself stationary. Such systems have utility for self-contained well equipment, but, due to the "capstan" effect in the curved tubing at the well entrance, they are not usually effective with wireline tools because of the tremendous forces necessary to pull cables through and around this curved entrance portion.
Thus, as explained more fully in U.S. Pat. Nos. 4,337,969 (issued July 6, 1982) and 4,349,072 (issued Sept. 14, 1982), both assigned to the Assignee of the present invention, it has been proposed to move conventional wireline tools through a deviated borehole by use of an extension member (a "stinger") affixed to the well-logging tool and movable into and out of the lower end of a pipe, such as drill pipe, in which it is carried to the borehole region of interest. As further described in these patents, the stinger then provides for pushing and pulling the well logging tool through this borehole region as desired.
A number of challenges, however, are associated with this technique. Principle among them is making the electrical connections between the logging tool in the borehole, the surface equipment at the top of the borehole, and the cable in between. It is impractical to attempt to feed the cable into the drill pipe as the drill pipe is added to the drill string one section at a time at the surface. One prior art solution was to attach the wireline to the outside of the drill pipe as the drill string was being assembled. Attaching the cable to the outside of the drill pipe, however, exposes it to a substantial risk of damage and abrasion as it is then moved through the borehole.
Another solution, as described in the above-noted '969 patent, is to secure the cable to the outside of the stinger, but pass the cable which is above the stinger through the inside of the drill pipe. This provides additional protection for the cable, but still does not enclose it fully all the way to the tool.
The above-noted '072 patent discloses another very successful method and apparatus for pulling the wireline cable through the drill pipe after the drill pipe has been assembled. A full-sized wireline tool (usually too big to pass through the drill string) is releasably attached to the bottom end of the drill string. A locomotive propelled by mud pressure in the drill string pulls both the wireline and the stinger through the drill string. The stinger then docks on the upper end of the wireline tool, to make the mechanical and electrical connections and to propel the tool out of the drill string and into the borehole on the end of the stinger. Again, this invention averts the need to install the wireline through the entire length of the drill string as it is being assembled. However, it is still necessary to provide the stinger, during assembly at the wellsite, with its own length of cable from end to end, which, in this case in installed inside the stinger where it is protected. Unfortunately, this latter feature makes it inconvenient to use stingers of substantial length, thus requiring a series of shorter logging operations over intervals of the length of the short stinger, rather than being able to conduct longer individual operations with a lengthy stinger. Perhaps an even greater factor limiting the practical length of the stinger is the risk that the stinger may buckle when being pushed out of the drill stem by the locomotive. The longer the stinger, the greater may be the necessary pushing force, and accordingly the greater the risk of buckling.
A need therefore remains for an apparatus and method for conducting logging or perforating operations in a highly-deviated well bore in which drill stems and stingers of practically any desired length can be assembled and used without requiring that they be "pre-wired" or otherwise furnished with a wireline cable, in which the wireline cable can be furnished to the logging tool through the drill stem and stinger to protect the cable from damage in the borehole, and in which the stinger is effectively pulled out from the drill pipe so that, regardless of the length of the stinger, it is essentially protected against buckling.